The songs you hear on your transistor, or the pictures you see on your TV are canied from the studios to your home on radiowaves. Telephone calls you make, on the other hand, are bansmitted by electric current flowing in copper wires. In-the recent past,-new technologies have sppeared for transmitting various kinds of electric signals on glass fibres. This has been possible due to the advances in fibre optics technology. Fibre optics is the technique of transmitting light waves through glass wires as thin as human hair. These wires called optical fibres could be made of glass or transparent plastic, quartz, nylon or polystyrene. Opticalfibres are thin hair-like solid strands that carry light along their length, by a process of multiple total internal reflections (Fig). We will not go into the details of the process. In this process the beam of light entering at one end is transmitted along the fibre, without loss of intensity, whether the fibre is straight or bent in a curve.